This invention relates generally to off-road motor vehicles, such as tractors, and more particularly, to a front power-takeoff drive connectable to a front mounted implement attached to the steerable axle of a compound steering mechanism.
Tractors, whether used in an agricultural setting or in an industrial setting, typically include a fixed axle through which primary driving power is transferred through fixed wheels rotatably mounted on opposing ends of the fixed axle, and a steering axle having pivotally mounted steerable ground engaging wheels rotatably mounted on the opposing ends thereof to support the chassis of the tractor above the ground. Although supplemental driving power is often provided to the steerable ground engaging wheels, a steering mechanism remotely controllable by the operator from the operator's compartment selectively controls the pivotal movement of the steerable wheels relative to the steering axle.
One such steering mechanism incorporates a transversely disposed, horizontally extending hydraulic cylinder supported by the steering axle and connected to the opposing steerable wheels. This hydraulic cylinder affects pivotal movement of the steerable wheels about their respective pivotal connections to the steering axle by manipulating the pressures in the hydraulic cylinder to effect a transverse extension of cylinder rod, causing a turning of the wheels.
Due to physical limitations relating to the range of movement of the steering mechanism and to the eventual interference between the steerable wheels and the chassis or the steering axle, the amount of pivotal movement of the steerable wheels relative to the steering axle is limited to a given turning angle. This maximum turning angle defines the minimum turning radius of the tractor for a given wheel base length and tread spacing. The selection of the length of the wheel base, i.e., the distance between the fixed axle and the steering axle, is a compromise between the need to minimize the turning radius and, therefore, minimize the wheel base length, and to maximize ride considerations which require longer wheel base lengths.
Because of the size and orientation of the axle support and oscillation components, known compound steering mechanisms, such as found in U.S. Pat. No. 5,297,648, granted on Mar. 29, 1994, to C. A. Hansen and J. C. Hurlburt, are not well suited for small tractors, particularly when front hitch and front PTO applications are desired. Economy is also a major concern with small tractors as the incremental cost of providing a compound steering mechanism becomes a greater percentage of the overall cost of the small tractor. By providing a compact pivotal support for the steerable axle and an oscillation stop package immediately behind the front axle, a front-mounted attachment could be brought closer to the axle and economies maintained.
In general, front hitches for tractors are increasing in popularity, particularly in European farming operations. The adaptation of a compound steering mechanism as disclosed in the aforementioned U.S. Pat. No. 5,297,648, cannot accommodate the use of a powered front-mounted implement as the structure of the tractor will not permit the passage of a power-takeoff shaft from the tractor engine to the implement. By mounting the implement directly to the steerable axle, the implement will pivot with the axle about its steering axis, meaning that the implement will move laterally with respect to the chassis and the tractor engine. This lateral movement of the front-mounted implement further complicates the problem of providing a power-takeoff drive thereto as the power-takeoff shaft must be able to swing laterally in unison with the front-mounted implement.